1. Field of the Disclosure
The disclosure refers to a vacuum pump, in particular a screw-type vacuum pump, a Roots vacuum pump or a rotary vane vacuum pump.
2. Discussion of the Background Art
Vacuum pumps comprise pumping elements arranged in a pumping chamber formed by the pump housing and serving to convey a fluid, especially a gas such as air. The pumping elements are usually driven by an electric motor. For a simple variation of the rotational speed of the vacuum pump it is known to use frequency inverters, so as to be able to change the motor speed in a simple manner. A frequency inverter is a sensitive electronic component. To allow a good cooling and a vibration-free arrangement of the frequency inverters, it is known to provide them in a control cabinet independent from the vacuum pump and separately from the pump. However, this is troublesome in particular because of the necessary wiring between the control cabinet and the electric motor of the vacuum pump. Therefore, it is generally preferred to arrange the frequency inverter directly at the vacuum pump.
For frequency inverters arranged immediately at the vacuum pump it is known to provide air cooling for the cooling of the frequency inverters. In this case, the cooling is effected using ambient air drawn by a blower and blown towards the frequency inverter. Thus, the cooling is achieved by forced convection. However, such air-cooling means are disadvantageous in that high protection ratings cannot be achieved or only with great effort. Even for lower protection ratings a complex housing is required. Especially in a dirty environment the maintenance effort is high, since frequent cleaning and filter changes are necessary. It is further known to cool the frequency inverters using natural convection, in which case the housing is immediately provided with cooling ribs. However, this design is only possible if the ambient temperatures are correspondingly low and the pump is operated in a performance range where the frequency inverter is not heated up much. Since a free inflow of air has to be guaranteed, a high risk of contamination exists for this design as well.
It is further known to provide the frequency inverter with immediate water cooling. In this case, the frequency inverter is connected with a cooled surface of the vacuum pump. However, this has a drawback that the frequency inverter is exposed to the vibrations of the vacuum pump.
Moreover, the cooling requirements of the vacuum pump and the cooling requirements of the frequency inverter have to correspond to each other.
The frequency inverter used thus has to be adapted to the corresponding requirements. It is further known to provide a separate cooling plate for the frequency inverter, which is connected to a separate cooling circuit.
This is an extremely complex solution. It is a general drawback of water cooling for a frequency inverter that at a high air humidity condensate can also form within the frequency inverter.
It is an object of the disclosure to provide a vacuum pump with a frequency inverter, wherein a reliable cooling of the frequency inverter is guaranteed.                disclosure        